1. Field of the Invention
This invention relates in general to an apparatus and process for welding thermoplastic members, and more particularly, to an apparatus and process for creating a flash-free weld.
2. Description of Related Art
In order to weld thermoplastic members, to be used in window or door frames, for example, machines are known in which the thermoplastic members are clamped, the ends of the members are softened by a heating plate, and the softened ends are joined. The resulting flash can be removed while the joint is still warm or machined off after the joint has cooled. If the flash is to be removed after the joint has cooled, the welded members are removed from the welding apparatus and then placed in a second machine in which a router, grinder, or knife blade is used to remove the flash. Depending on the profile of the member, e.g., the inside surface where the window glass will rest, an additional step of removing some of the flash by hand may be necessary. Still other systems choose to remove the flash from the entire profile by hand.
If the flash is removed while still warm, often deformation in the zone of the weld results. To prevent this deformation, other systems, such as that disclosed in U.S. Pat. No. 4,239,574, use a two-step process of first, pinching the flash, and second, manually dragging a scraper around the edges of the joint to remove the remaining flash. The '574 patent discloses a guide means to guide the scraper around the area of the weld, but the actual removal of the flash is not caused by the welding head, but by a manual scraper. All these systems require additional time, effort, and apparatus to remove the flash after the weld is formed.